1. Field of the Invention
This invention relates to an illuminating apparatus, and particularly to an improvement in the optical characteristic of an illuminating apparatus narrowly limited in the opening area thereof, and a photographing apparatus provided with the illuminating apparatus.
2. Related Background Art
Regarding an illuminating apparatus used in a photographing apparatus such as a camera, various propositions have heretofore been made in order to cause beams emitted from a light source in various directions to be efficiently condensed within a necessary irradiation angle of view. Particularly in recent years, there has been proposed an illuminating apparatus in which instead of a Fresnel lens heretofore disposed in front of a light source, an optical member such as a prism or a light guide utilizing total reflection is disposed to thereby achieve an improvement in light condensing efficiency and the downsizing of the apparatus.
On the other hand, in an illuminating apparatus of a fixed irradiation range type, along with the higher magnification zoom of the photographing apparatus, illumination is effected to an unnecessary range in a telephoto state in which the irradiation range is narrow, and the loss of energy occurs, and in order to eliminate this phenomenon, there have been proposed such various illuminating apparatuses of a variable irradiation angle type as effect illumination corresponding to the conventional photographing range.
As the known technique of an illuminating system to which the technique as described above is applied, as is disclosed in the applicant""s Japanese Patent Application Laid-Open No. 2001-66672 (U.S. Pat. No. 6,400,905), there is an illuminating apparatus which comprises an optical prism disposed forwardly of a light source for totally reflecting at least some of an incident beam and making all of it parallel to an optical axis, and first and second optical panels disposed on the object side of the optical prism, and in which the irradiation angle is varied by a change in the relative position of these two optical panels.
In photographing apparatuses such as cameras in recent years, the downsizing and lighter weight of the apparatus progress and on the other hand, the photo-taking lenses thereof are in a tendency toward higher magnification zoom. Generally, the photo-taking lenses of such photographing apparatuses tend to gradually become darker due to downsizing and higher magnifications, and when photographing is effected without the use of an auxiliary light source, there has been the possibility of hand vibration or the like adversely affecting the result of the photographing. From such a background, usually, an illuminating apparatus as an auxiliary light source is contained in a photographing apparatus such as a camera, but from the situation as described above, the frequency of use of the auxiliary illuminating apparatus has been greatly increased as compared with the prior art and the quantity of emitted light required for one shot has been in a tendency toward increase.
From such a tendency, in the above-mentioned Japanese Patent Application Laid-Open No. 2001-66672, the illuminating apparatus is comprised of an optical prism disposed forwardly of a light source for totally reflecting at least some of an incident beam and making all of it parallel to an optical axis, and first and second optical panels disposed on the object side of the optical prism, and the irradiation angle is adapted to be varied by a change in the relative position of the two optical panels.
In the illuminating apparatus of such a construction, however, there have been left the problems that three optical members are required in order to effect the condensing and diffusion of illuminating light and the number of parts becomes great, that the optical prism for constituting a condensing optical system becomes bulky and the general shape of the optical system becomes bulky, and that the positional accuracy of the arrangement of the many optical parts required becomes necessary and therefore the assembling work becomes complicated.
As described above, the conventional condensing optical system has suffered from problems in respect of arrangement space, the complicatedness of the assembling work, etc., and it is difficult to construct an optical system which can be made compact without the optical characteristic thereof being deteriorated. On the other hand, in such an illuminating apparatus wherein the irradiation angle is variable, it is true that when the optical system is located at a position corresponding to the telephoto side, it is necessary to effect illumination in its most condensed state, and unless all surfaces in the limited opening area are effectively utilized, the originally required guide number cannot be obtained. From this, it becomes a requisite task that the tasks of downsizing and improved optical characteristic are realized at a time.
The present invention has been made in view of such problems and has as its object to provide an illuminating apparatus of a simple construction which can efficiently utilize light from a light source and can contribute to space saving, and a photographing apparatus provided with the same.
So, one aspect of the present invention is an illuminating apparatus comprising:
a light source; and
an optical unit disposed on the object side of the light source;
the optical unit being provided with a lens portion having positive refractive power in the central portion thereof, incidence surfaces on both sides of the lens portion on which light from the light source is incident, a reflecting surface for totally reflecting the light incident on the incidence surfaces, and an emergence surface from which the light reflected by the reflecting surface emerges;
wherein a beam emerging from the lens portion and a beam emerging from the emergence surface intersect with each other substantially at the same place in their condensed states.
The illuminating apparatus further comprises a second optical unit disposed on the object side of the optical unit, and the relative interval between the optical unit and the second optical unit is changed, and an irradiation angle is changed.
Also, the second optical unit is provided with a second lens portion having positive refractive power in the central portion thereof, and a plurality of prism portions having their convexity facing the object side on both sides of the second lens portion.
Also, the second optical unit is provided with a reflecting surface for totally reflecting some of a beam emerging from the optical unit by the side thereof, and directing it to the plurality of prism portions. The light reflected by the reflecting surface of the second optical unit and directed to the plurality of prism portions travels in a direction substantially parallel to the optical axis of the second optical unit.
When the angle formed by the optical axis side surface of the plurality of prism portions with respect to the optical axis is defined as xcex8, the following condition is satisfied:
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Also, the light source is a cylindrical light emitting tube, and the lens portion of the optical unit is of a cylindrical lens shape of which the lengthwise direction is the same direction as the lengthwise direction of the light emitting tube.
Also, the light source is a cylindrical light emitting tube, and the lens portion of the optical unit is of a cylindrical lens shape of which the lengthwise direction is the same direction as the lengthwise direction of the light emitting tube. The second lens portion of the second optical unit also is of a cylindrical lens shape of which the lengthwise direction is the same direction as the lengthwise direction of the light emitting tube. Further, the ridgeline of each of the prisms of the second optical unit is parallel to the lengthwise direction thereof.
Also, the light source is a cylindrical light emitting tube, and on the optical axis of the optical unit in a plane perpendicular to the lengthwise direction of the light emitting tube, the beam emerging from the lens portion and the beam emerging from the emergence surface intersect with each other in their condensed states.
Also, the illuminating apparatus further comprises a member disposed at a location on the light source which is opposed to the optical unit for reflecting the light from the light source.
Further features of the present invention will become apparent from the accompanying drawings and the following description.